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WASHINGTON — The Food and Drug Administration has updated the label of Merck's cervical cancer vaccine Gardasil, adding new information about its protective effects against two other gynecological cancers.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The new labeling indicates the vaccine also protects against cancers of the vagina and vulva, which affect more than 5,000 women in the U.S. each year, according to Merck.

The vaccine works by defending against four strains of the human papillomavirus, which cause the majority of cervical cancers. A Merck scientists said the virus accounts for a smaller portion of vaginal and vulvar cancers, though he added it plays a role in more than half of them.

"Anytime we have evidence of additional cancer protection, that's a really important piece of information," said Merck's Rick Haupt, executive director for HPV vaccines.

It was not immediately clear what the additional indication would mean for sales of the vaccine, which have fallen short of the company expectations.

Merck has already scaled back full-year sales estimates for Gardasil from between $1.9 billion and $2.1 billion to between $1.4 billion and $1.6 billion, following regulatory setbacks and challenges making inroads with young adult patients.

First approved in 2006, Gardasil is the only cervical cancer vaccine approved for the lucrative U.S. market, though Merck has had limited success expanding use.

The FDA
rejected Merck's proposal
in June to begin marketing the vaccine to women ages 27 to 45. It is currently approved for ages 9 to 26. The company's expansion effort seems even less likely after a government-funded study released last month concluded the roughly $375 vaccine is not cost-effective for women in their 20s and older.

Gardasil is outselling rival GlaxoSmithKline's Cervarix vaccine abroad. The Glaxo injection is still pending review at the FDA.

The positive announcement Friday breaks a string of FDA rejections for the Whitehouse Station, N.J.-based company. Earlier this year the agency denied applications to sell two new experimental cholesterol drugs and what would have been the first nonprescription cholesterol drug.

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